co-habiting females - why do their periods coincide?

Factual Questions
1

emm…thats it. Why?

Sorry if this is a dumb male question but I really don’t know why. Ive lived with groups of females in the past however and it does seem to happen.

Are they more psychic or something?

2

http://www.straightdope.com/classics/a2_306.html

3

Thanks for the link.

So even Cecil thinks its a “complete mystery”.

That doesn’t bode well.

4

The “why” is still something of a mystery, however, the mechanism has been found:

Stinkin’ Synchin’

I’ve seen another study that found that pheremones released at one point in the menstrual cycle elongated the recipients cycle; and that other times the pheremones shortened the cycle.

5

I heard that in any group of females living together, that one was the dominant female and the other females would have periods to coincide with hers. For instance, daughters will synch with mother, and so forth.

6

Hell, we didn’t even LIVE together, but my best friends and I would always get our periods around the same time.
Maybe we should survey us female Dopers-see what times we get our periods?

7

It’s never happened to me, in all the years I lived with my mother, or after when I shared with female friends. I guess it must happen to some, but not to all.

8

You would also have to take into account those of us who are on birth control pills, and therefore have “fixed” periods.

9

I was teasing, actually.